(1) Field of the Invention
The present invention relates to one end-sealed ceramic double wall-structural tubes in which inner and outer tube members are integrally connected with each other by means of a plurality of supporting portions, and to a process for producing the same.
(2) Related Art Statement
When double wall-structural tubes in which an outer tube member and an inner tube member are integrally connected with each other through supporting portions are to be extruded, it has been impossible to obtain, by a single extrusion step, a double wall-structural tube in which an end of the tube, particularly an end of the outer tube member only is sealed.
For this reason, when an end face of an integrally extruded ceramic double wall-structural tube, particularly an end portion of its outer tube member only needs to be sealed, it is a conventional practice that a dried member having a peripheral edge of the same shape as that of an end portion of the tube to be sealed and the same composition as that of the tube is separately formed, and is fixed to the end face of the dried tube, which is fired to effect integration at the end portion of the tube.
However, the above-mentioned conventional end face-sealing process requires use of a member having the same composition as that of a double wall-structural tube and exhibiting, when dried, a given shape to seal an end of the tube. As a result, a gap is formed between the end of the tube and the sealing member in the tubular product integrated by firing. Thus, this unfavorably hinders complete integration. Consequently, ceramic double wall-structural tubes having such ends are likely to be broken, and are low in reliability.